Gasoline Engine Exhaust Profile
OTHERS – POSSIBLE CARCINOGEN (IARC 2B)
Gasoline Engine Exhaust Profile
- A complex mixture of gases and particulate matter produced when gasoline fuel combusts
- Associated cancer: Lung cancer (limited evidence)
- Most important routes of exposure: Inhalation
- Primary sources: Cars, power generators, and hand-held equipment (ex. chainsaws) that use gasoline engines
- Occupational exposures: Those who work with or near machines that use gasoline engines, such as professional drivers, border inspectors, and tollbooth workers, are at highest risk of exposure
- Environmental exposures: Proximity to traffic increases exposure; those walking, cycling, driving, working, living, or attending school on or near major roadways are more likely to be exposed
- Fast fact: Traffic emissions can infiltrate buildings; for example, vehicle emissions can account for up to half of indoor ultrafine particle mass.
Gasoline engine exhaust, produced when gasoline fuel combusts, is a complex mixture of gases (e.g. carbon monoxide, nitrogen oxides, and volatile organic compounds) and particulate matter (e.g. elemental and organic carbon, ash, sulfate, and metals). The composition of gasoline engine exhaust depends on a number of factors, including the formulation of the gasoline being burned, mechanical characteristics and age of the engine, vehicle weight and speed, pattern of use, maintenance, and emission control systems.[2,3] Gasoline and diesel engine exhaust contain similar gases and particulate matter but in different proportions. Generally, compared to diesel engines gasoline engines emit more carbon monoxide and hydrocarbons, and less particulate matter, nitrogen oxides, carbon dioxide, and sulfur compounds.
In 2013, the International Agency for Research on Cancer (IARC) classified gasoline engine exhaust as possibly carcinogenic to humans (Group 2B). This classification was based on inadequate evidence of carcinogenicity in humans, a reflection of the difficulty in separating effects of diesel and gasoline exhaust. There was sufficient evidence that the condensates of gasoline engine exhaust can cause lung cancer in experimental animals.
Short-term exposure to gasoline engine exhaust may irritate the eyes, nose, or throat, aggravate existing respiratory allergies, and lead to headache, light-headedness, or tingling extremities. Long-term health effects have been assessed through epidemiological studies examining proximity to road traffic. The associated long-term health effects include increased illnesses related to respiration and aggravated asthma in children, decreased cardiovascular health, and worsened symptoms in those with existing heart and lung conditions.
Regulations and Guidelines
Occupational Exposure Limits (OEL)
There are no occupational exposure limits established at federal or provincial levels for gasoline engine exhaust. However, occupational exposure limits for components of gasoline engine exhaust (such as carbon monoxide or particulate matter) exist within provincial and federal environmental legislation.
Environment Canada Guidelines
The Canadian Environmental Protection Act (CEPA) outlines a number of regulations that influence gasoline engine exhaust emissions. They include:
|Benzene in Gasoline||1997|
|On-Road Vehicle & Engine Emission||2002|
|Off-Road Small Spark Ignition Engine Emission||2003|
|Marine Spark-Ignition Engine & Off-Road Recreational Vehicle Emission||2011|
|Sulphur in Gasoline||1998|
Gasoline Fuel Use in Canada
Gasoline engines are used in cars, power generators, and hand-held equipment such as chainsaws and leaf blowers.
On average, 60% of gasoline consumption in Canada occurs in Ontario and Quebec, 32% in the western provinces, and 8% in the Atlantic provinces and territories. In 2014, approximately 43.4 billion litres of gasoline were sold for road motor vehicles in Canada.
Regulations regarding fuel composition and emission standards in Canada (aligned with the US Environmental Protection Agency) should result in lower gasoline exhaust emissions across North America. The Sulphur in Gasoline Regulation, for example, requires that sulphur content be lowered gradually to a level of 10 ppm by January 2020. Lower sulphur content in the fuel leads to lower emissions of particulate matter in the exhaust. Furthermore, numerous regulations have been developed – and others are under review – that outline allowable emissions for new models of on- and off-road vehicles and engines.[8,11,12]
In order to reduce harmful exhaust emissions, newer gasoline engines in cars have been fitted with electronic feedback control systems, port fuel injection, and three-way catalyst systems. These are technologies that reduce emissions of particulate matter, nitrogen oxides, carbon monoxide, non-methane hydrocarbons, and unregulated emissions.
Environmental Exposures Overview
Exposure to gasoline engine exhaust in the general population increases with proximity to traffic. In calm conditions, emissions accumulate near roadways; concentrations of carbon monoxide, metals, and particulate matter decline sharply approximately 300 metres from the road. Children who live in homes or go to schools that are located downwind from major highways are more likely to be exposed to gasoline engine exhaust. Traffic emissions can infiltrate buildings; for example, vehicle emissions can constitute 24-47% of indoor ultrafine particle mass. In addition, individuals are more likely to be exposed if walking or cycling by the roadside and in high traffic conditions.
Because Canadians spend close to 90% of their day indoors, exposure in indoor environments is an important consideration.[1,20] Factors that influence indoor gasoline engine exhaust concentrations include the air exchange rate in the building and whether it has an attached garage. Greater rates of air exchange mean there is a greater influx of air from the outdoors, which leads to greater contributions of outdoor sources to indoor environments. Having an attached garage can lead to increased exposure since contaminants can more readily enter the house. For example, in Canada, benzene levels are three times higher in homes with attached garages compared to those with detached or no garages. The presence of benzene is attributable to engine exhaust, as well as to the evaporation of benzene from gasoline.
Lastly, time spent in vehicles contributes a large proportion of total exposure to gasoline engine exhaust in adults. Higher emissions are reported on arterial roads, where there is constant stopping and acceleration due to traffic lights. This is because fast acceleration increases the amount of exhaust produced.
Occupational Exposures Overview
Inhalation is the primary route of occupational exposure to gasoline engine exhaust.
A diverse group of professions can be occupationally exposed to gasoline engine exhaust. These include, in decreasing order of exposure level: professional drivers, border inspectors, tollbooth workers, car mechanics, service station attendants, street workers, traffic police, car park attendants, and shopkeepers. Exposures also occur when workers use portable, engine-powered tools.
CAREX Canada has not prioritized gasoline engine exhaust for exposure estimate development. This is because a lack of exposure data precluded it in the past. However, the team is investigating new sources of data and methods in order to potentially address this exposure in the future.
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